Technologies and methods exist for spray painting a variety of coating materials on a wide range of commercial and non-commercial products. These methods include airless, high-pressure air, powder coating, electrostatic, and high-volume, low-pressure (HVLP) spraying.
Transfer efficiency is defined as the percentage of sprayed product that adheres to the intended target. High-pressure air application techniques typically have a transfer efficiency (TE) of 35%. The amount of sprayed product that does not adhere to the target (100%-TE) is known as “overspray.” By way of illustration, a high-pressure air application technique with a TE of 35% would have 65% overspray. The overspray consists of small droplets that can travel significant distances before being deposited onto the ground, water, or other surfaces.
HVLP spray painting technology provides increased transfer efficiency, typically 60 to 70% TE, with only 30 to 40% overspray.
Most paint and other coating materials, including waterborne paint, contain varying amounts of volatile organic compounds (VOCs). Volatile organic compounds are regulated as hazardous to the environment and are considered by many in the scientific community to be significant contributors to global warming and ozone depletion. Furthermore, volatile organic compounds released from paint overspray contribute to the formation of smog. Sunlight reacts with volatile organic compounds to create ground level smog. Smog is believed to contribute to lung disease.
Human exposure to volatile organic compounds can cause headaches, eye irritation, nausea, dizziness, and fatigue. Paint technicians exposed to volatile organic compounds for an extended period of time can suffer permanent damage to the central nervous system, liver, and kidneys.
Every year in the United States alone, millions of pounds of spray painted coatings containing volatile organic compounds are applied. Traditionally, spray painting operations involving motor vehicles take place inside approved spray booth structures, which are regulated, in the United States, by the Environmental Protection Agency (EPA), the National Fire Protection Association (NFPA), and the Occupational Safety and Health Administration (OSHA).
Approved spray booth structures contain filter elements that capture overspray, which, if not captured by abatement means, becomes fugitive (airborne) and hazardous to the environment. However, there are many small re-finish type repairs performed to motor vehicles not within the confines of an approved spray booth. Additionally, there are numerous non-automotive spray painting operations performed outdoors or in non-approved indoor areas.
Non-limiting examples of non-automotive spray painting operations in which products containing volatile organic compounds are sprayed outside of an approved spray booth include structural steel and interior painting on large commercial buildings, water towers, signal towers, bridges, commercial and non-commercial boats and ships, railroad equipment, on-site commercial office furniture finishing and re-finishing, commercial and residential bathroom fixture re-finishing, commercial and non-commercial aircraft finishing and re-finishing, residential housing exterior and interior painting, commercial and noncommercial sign painting, agricultural equipment re-finishing, and motorcycle refinishing.
Many spray painting operations are performed outside of a spray booth because it is either impractical or impossible to place the object to be painted into a spray booth. Even when it would be practical to place an object in a spray booth, spray booths meeting the regulatory requirements are expensive to purchase and install.
There are many operations other than painting which involve spraying in which it is desirable to capture overspray. A few non-limiting examples include operations involving the spraying of hair spray, biocides, cleaners and sun-independent skin tanning agents.